Actuators are installed in an aircraft to drive an airfoil, a taking-off and landing unit and so on. The actuator is repaired or replaced when it fails or reaches repair timing. The repair timing is typically determined by a serviceman based on a past repair record.
However, strictly, operation records differ from each other for every aircraft. Therefore, there is a possibility that the actuator fails prior to previously set repair timing. Also, there is a case that the actuator can be used sufficiently even if the previously set repair timing has passed away. Therefore, the technique which can estimate the lifetime of the actuator in a high precision is demanded.
Patent Literature 1 discloses a technique that can know the exchange timing of the actuator even if the aircraft is in a flight condition. Specifically, a position sensor attached to the actuator detects a position of a piston of the actuator and outputs a position signal to a control unit. The control unit calculates a movement amount of the piston of the actuator based on a position signal. When a total movement amount of the piston of the actuator exceeds a preset threshold value, the control unit outputs a notice signal. The notice signal is outputted even if the aircraft is in the flight condition.